Audio signal transmitting system

ABSTRACT

In an audio signal transmitting system having an audio signal transferring device and a loudspeaker to reproduce audio signals, the system includes a vibrato device consisting of a charge transfer device (CTD) connected to the transferring device, a clock pulse oscillator to produce clock pulses and supply the clock pulses to the CTD, and an oscillator to supply low frequency signals. The clock pulse oscillator is controlled in its frequency in response to the low frequency signals, so that delayed and frequency-modulated audio signals are reproduced by the loudspeaker.

I Unlted States Patent 1 1 1111 3,878,472

Osakabe Apr. 15, 1975 [54] AUDIO SIGNAL TRANSMITTING SYSTEM 3,749,8377/1973 Doughty 84/l.25 X Inventor: os o Osakabe, okohama, Japan3,761,631 9/1973 lto et al. l79/lOO.l TD X CATl .[73] Asslgneez SonyCorporation, Tokyo, Japan OTHER PUBU Gllder, Bucket-Br1gade Device Sa1dto Cut Aud1o Flledi 1973 Delay-Line Costs Drastically, Electronic Design24, 21 APPL NO; 421 215 November 25-, 1971, p. 34.

Primary ExaminerJames B. Mullins [30] Forelgn Apphcamm Pnonty DataAttorney, Agent, or Firm-Hill, Gross, Simpson, Van

Dec. 11, 1972 Japan 47-1422221U] Santen, Steadman, Chiara & Simpson [52]US. Cl 330/124 R; 84/1.25; 84/D1G. 26; [57 ABSTRACT 84/D1G. 27; 179/1 6;179/1 J; 328/56 I It t h a [51] Int. Cl. H03f 3/68 anlau lofslgtla g 2 g1 u 10 581 Field of Search 330/124 R; 179/1 G, 1 J, sgna l 179 duceaudlo signals, the system lllClUdCS a v1brato de- /lO0.1 TD, 100.4 ST,84/1.25, DIG. 1, DIG 26 DIG 328 v1ce cons1st1ng of a charge transferdev1ce (CTD) connected to the transferrmg devrce, a clock pulseosclllator to produce clock pulses and supply the clock [56] Referencescued pulses to the CTD, and an oscillator to supply low fre- UNITEDSTATES PATENTS quency signals. The clock pulse oscillator is controlled3,160,695 12/1964 Bonhamw 84/1.25 in its frequency in response to thelow frequency sigfif fi nals, so that delayed and frequency-modulatedaudio l 61' l d k 3,686,471 8/1972 Takahashi.. 179/100.4 ST Sgnals arereproduced by the spea er 3,719,782 3/1973 Barnum 179/1 J 9 Claims, 9Drawing Figures Ass 29.

AUDIO SIGNAL TRANSMITTING SYSTEM BACKGROUND OF THE INVENTION l. Field ofthe Invention The present invention relates generally to an audio signaltransmitting system. and more particularly to an audio signaltransmitting system in which a vibrato is caused in a sound.

2. Description of the Prior Art A microphone mixing circuit has beenknown as a circuit by which a user's voice is reproduced from a speakerwith the background music of. for example. a phonograph record. However.with the microphone mixing circuit of the prior art. outputs from one ortwo microphones are added. as they are. to left and right channelsignals of a stereo-phonograph as monoral or stereo. so that the voicereproduced from the speaker is poor as compared with that of theprofessional singer from the phonograph record.

In general. it is said one attribute of a good singer is that the goodsinger can apply a vibrato to his voice. However. it is generallydifficult to artificially treat a voice. which is once emitted to aspace. to obtain a specific effect. In order to produce. for example. anatmosphere like a concert hall. when an unskillful person sings in aroom with a good residual sound effect. his singing voice can be heardby a listener as a superior voice due to the residual sound effect.However. it is. in general. almost impossible to prepare such a room asa concert hall in an ordinary house. from an economical point of view.

Such a method is also proposed wherein a voice signal of a person from amicrophone is delayed through a delay device mechanically and thenreproduced by a speaker. but in this case a sound peculiar to themechanical delay device is produced by the speaker.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a novel audio signal transmitting system with a vibrato device.

Another object of the invention is to provide an audio signaltransmitting system which has a device for delaying an audio signal andapplying thereto a vibrato, so that a singer himself or a listener canenjoy a pleasing musical tone.

A further object of the invention is to provide an audio signaltransmittinng system with a device which can be applied to a so-calledmixing apparatus and with which a person can mix his voice with musicfrom a music source such as a phonograph record. a broadcasting or thelike. which makes is possible for a vibrator to be applied to theperson's voice or singers voice of the music source.

A further object of the invention is to provide an audio signaltransmitting system in which a voice emitted once to a space is pickedup by a microphone and a vibrato is applied thereto by electricallytreating the audio signal.

A yet further object of the invention is to provide an audio signaltransmitting system with a novel vibrato device which can change itsvibrato in response to the intensity of an audio signal.

A still further object of the invention is to provide an audio signaltransmitting system in which. instead of the center vocal sound from astereo source. a vocal sound supplied with a vibrato from a microphoneis inserted.

The additional and other objects. features and advantages of theinvention will be apparent from the following description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I diagrammatically illustrates apreferred embodiment of an audio signal transmitting system according tothe present invention.

FIG. 2 is a circuit diagram showing the delay unit of the example shownin FIG. I;

FIG. 3A and 3B are waveform diagrams for illustrating clock pulsessupplied to the delay unit shown in FIG. 2;

FIG. 4 is a graph illustrating the relationship of a low frequencysignal. the frequency of the clock pulses and the delay time of an audiosignal;

FIG. 5 diagrammatically illustrates a second embodiment of the inventionin which the output signal from a microphone is delayed and suppliedwith a vibrato. and thereafter mixed with a stereophonic signal;

FIG. 6 diagrammatically illustrates a third embodiment of the inventionin which one of two signals combined with stereophonic signals isdirectly mixed with an output signal from a microphone and in which theother signal is mixed with an output signal from the microphone which isdelayed and subjected to a vibrato;

FIG. 7 diagrammatically illustrates a fourth embodiment of the inventionin which the center vocal of a stereophonic signal is supplied with avibrato: and

FIG. 8 diagrammatically illustrates a device used in the fourthembodiment by which a vibrato is varied in response to the magnitude ofan audio signal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of thepresent invention will now be described with reference to FIG. I. In theembodiment of FIG. I. left and right stereophonic signals are reproducedfrom a stereophonic signal source such as a phonographic record 1 by acartridge 1a. The left channel signal L is applied to an equalizeramplifier 2L, amplified therein in equalizing manner, applied to a mixercircuit 3L and then applied to a main amplifier 4L. The output signalfrom the main amplifier 4L is fed to a left speaker 5L to be reproduced.While, the right channel signal R is applied to an equalizer amplifier2R to be amplified in equalizing manner, to mixer circuit 3R, to amain'amplifier 4R to be amplified in power, and then to a right speaker5R to be reproduced. The output signal from a microphone 6 is fedthrough a microphone amplifier 7 to the mixer circuit 3L to be combinedwith the left channel signal L, and is also applied to a vibrato device10 directly. In this case, the output signal from the microphone 6 isfed to a variable delay unit to be delayed, and the delay time thereofis varied periodically to achieve a so-called frequency modulation.Thus, a vibrato is applied to the output signal from the microphone 6.

This will now be described in detail. The vibrato device 10 includes amicrophone amplifier II to which the output signal from the microphone 6is applied. The amplified output signal from the amplifier 11 is therfed to a variable delay unit 12 to be delayed and frequency-modulated.The output signal from the delay unit 12 is fed through a bufferamplifier 13 and a lowpass filter 14 to the mixer circuit 3R to be mixedwith the right channel signal R.

As seen in FIG. 2, the variable delay unit 12 is provided by abucket-brigade device. which will be hereinafter referred to as BBD. TheBBD 12 as shown in FIG. 2, employs n FETs. T, to T,, which are connectedso that their drain and source electrodes are connected with one anotherin series. The drain electrode of the FET T, is connected to an inputterminl 21 of the BBD l2 and the source electrode of the FET T isconnected to a power source terminal 22 of the BBD 12 to which a powersource of -B potential is connected. Between the input terminal 21 and aground terminal 23 of the BBD 12. there is inserted a capacitor CCapacitors C to C,, are connected between the source and gate electrodesof the FETs T, to T,,, respectively. and the gate electrodes of the oddnumbers FETs T T are connected to a first clock pulse input terminal 24of the BBD 12, while the gate electrodes of the even numvers FETs T Tare connected to a second clock pulse input terminal 25 of the BBD 12.The source electrodes of the FETs T,, and T are connected throughsource-follower FETs Ta and T,, to an output terminal 26 to the BBD 12.The part of the BBD 12 just mentioned above or the part shown by adotted line block in FIG. 2 is made as an integrated circuit.

A clock pulse oscillator 15 of the BBD 12 produces first and secondclock pulses (synchronizing pulses) Pa and Pb which are shifted in phaseby l80 as shown in FIGS. 3A and 3B with each other, and are fed to theterminals 24 and 25, respectively. The terminal voltage across thecapacitor C O is varied in accordance with the signal from the amplifier11. When the pulse Pa is applied to the terminal 24, the FET T is turnedON. Accordingly. the charge stored in the capacitor C O is shifted ortransferred to the next capacitor C 1 through the FET T,. Thereafter.when the pulse Pb is applied to the terminal 25, the FET T is turned ON.Thus. the charge stored in the capacitor C l is transferred to thefollowing capacitor. C through the FET t When the pulse Pa is nextapplied, the FET T is turned ON to transfer therethrough the chargestored in the capacitor C; to the capacitor C At this time. since theFET T is turned ON also. the charge newly stored in the capacitor C inresponse to the input signal is transferred to the capacitor C throughthe FET T The above operation is carried out repeatedly in response tothe pulses Pa and Pb. so that delayed signals can be delivered to theoutput terminal 26.

In this case. the charges stored in the capacitors C to C,, aretransferred at every supply of the pulses Pa and Pb, so that the delaytime becomes long as the frequency of the pulses Pa and Pb is low andthe number of the capacitors C to C is large. If n 256 and the frequencyof the pulses Pa and Pb is IOKHz. by way example. the delay time becomesto 12.8 milliseconds.

In order to vary the delay time of the BBD l2 periodically. a variablefrequency oscillator formed. for example. of an astable multivibrator isused as the clock pulse oscillator 15, and in order to control thevariable frequency oscillator 15 there is provided a low frequencyoscillator 16 which produces. for example. a sine wave signal 5,. (referto FIG. 4) with a frequency of 7H2. The sine wave signal S,- from theoscillator 16 is applied to the clock pulse oscillator 15 to control theoscillation frequency of the latter. Thus, as shown by a solid line inFIG. 4, the frequency f,, of the pulses Pu and Pb from the oscillator 15is periodically varied with the frequency 7Hz of the signal S as itsfrequency between IOKHz and 30 KHz in response the level of the signalS... or the pulses Pa and Pb are frequencymodulated with the signal S,..

When the frequency of the clock pulses Pa and Pb are periodically variedwith the signal S... the delay time T of the BBD 12 is also periodicallyvaried with the frequency 7H2 of the signal S as its frequency between.for example. 60 milliseconds and 20 milliseconds. Accordingly. the voicesignal from the microphone 6 is delayed in the BBD 12 at least 20milliseconds and varied in delay time between 40 milliseconds and 0.That is. the voice signal from the microphone 6 is delayed andfrequency-modulated in the BBD 12, so that the BBD 12 produces a secondsignal which is delayed and caused to be a vibrato.

As mentioned above, the output signal from the microphone 6 is delayedand caused to have a vibrato effect in the BBD 12 and thereafter mixedto the right channel signal R in the mixer circuit 3R. The low-passfilter 14 serves to eliminate the components of the pulses Pa and Pbcontained in the output signal from the BBD 12 through the amplifier 13.In this case, the left channel signal L is mixed with the output signalfrom the microphone 6 without being delayed, so that the left speaker 5Lproduces the user's singing voice with the music from the phonographicrecord 1 as background. while the right speaker 5R produces the userssinging voice with the music from the record 1 as background. whichvoice is delayed and caused to have a vibrato effect.

When the singing voice which is not delayed and the voice which isslightly delayed and caused to have a vibrato effect are reproduced atthe same time. a peculiar effect can be achieved, which is somewhatdifferent from the effect achieved by applying an echo or reverberationto a professional singer in a popular song.

Further, since the singing voice without being delayed and the singingvoice being delayed and caused to have a vibrato effect are separatelyreproduced from the left and right speakers 5L and SR. the singing voicearriving at the left ear of the listener oruser always differs from thatarriving atthe right ear. or if the user with the microphone 6 moves inhis body when he sings, the reproduced voices arriving at high left andright ears become different further. Therefore, a sound effect which cannot be attained by the prior art microphone mixing circuit is obtainedby the present invention.

It is also possible that if a professional singers voice exists in theleft and right signals L and R reproduced from a record. a chorus of theusers voice with the singer's voice can be obtained.

A second embodiment of the invention will now be described withreference to FIG. 5 in which reference numerals the same as those of theforegoing figures indicate the same elements.

In the embodiment of FIG. 1, the voice signal which is not delayed isfed to the left channel signal L and the voice signal which is delayedand caused to have a vibrato effect is fed to the right channel signalR. However, in the embodiment of FIG. 5, a voice signal which is delayedand caused to have a vibrato effect by the same vibrato device 10, isfed to both of the left and right channel signals L and R. respectively.In this case.

it is also possible that. through the amplifier 7. a voice signalwithout being delayed can be applied to both the channel signals L andR. as shown by a dotted line in FIG. 5.

A third embodiment of the invention will now be described with referenceto FIG. 6. in which the same reference numerals or characters as thoseof the above fig- -ures show the same elements.

In the third embodiment of FIG. 6. if a professional singers voicesignal exists in the left and right channel signals L and R reproducedfrom the record 1. the voice signal is eliminated and in place thereof ausers voice signal which is subjected to vibrato is inserted. That is. amatrix circuit 8 is provided which is supplied with the signals L and Rthrough the amplifiers 2L and 2R. respectively. and produces signals L yR and R y L where the condition I y I 1 is satisfied. The mixer circuits3L and SR are supplied with the signals L 'y R and R 'y L. respectively.and also with the output signal from the microphone 6 through theamplifier 7 and the vibrato device 10. respectively.

In this case. consideration is given to a signal component in a programsource such as a record. A professional singers voice (center vocal) isrecorded with the same phase and level with respect to the left andright channels so as to be localized at the center of stereophonicapparatus. while a sound from a musical instrument is recorded in adifferent level with respect to the left and right channels so as to belocalized in dispersed left and right directions. Accordingly. if thematrices of L y R and R 'y L are carried out in the matric circuit 8.the signal from the muscial instrument is almost kept at the same levelas it is. but the professional singer's voice signal is cancelled if l'yl I and hence the signal from the musical instrument is only containedin the signals L 'y R and R y L. As a result. the user's voice isreproduced from the speakers L and SR instead of the professionalsingers voice. In this case. in addition thereto. the user's voice whichis not delayed is reproduced from the speaker 5L and the users voicewhich is delayed and caused to have a vibrato effect is reproduced fromthe speaker 5R. as described above. with the result that the microphonemixing effect is much enhanced.

Further. if the condition 1 'y is satisfied. the singer's voice isreproduced lower in response to y. a chorus of the users voice with thesinger's voice can be played.

FIG. 7 shows a fourth embodiment of the invention in which the partscorresponding to those of the above embodiments are shown with thecorresponding references. With the embodiment of FIG. 7, the singingvoice of a professional singer from the record 1 can be caused to have avibrato effect. That is. the sum signal L+R of the signals L and R isobtained from the matrix circuit 8 and then applied to an audioband-pass filter 9 from which the vocal signal of the singer is derived.The thus derived vocal signal from the bandpass filter 9 is directly fedto the mixer circuits 3L and 3R. respectively. and also to the vibratodevice 10. The signal which is delayed and caused to have a vibratoeffect from the vibrato device 10 is fed to the mixer circuits 3L and3R, respectively. Accordingly. from the speakers 5L and SR. there arereproduced both the original singing voice and that delayed and causedto vibrato of the singer with the music as its background.

In the above embodiments. the intensity or amount of vibrato issubstantially constant. but it is possible to have the intensity oramount of vibrato changed in response to the magnitude of the audio(vocal) signal to enhance the vibrato effect. With reference to FIG. 8.in which the parts similar to those of FIG. I are shown with the similarreference numerals. such a vibrato device 10 will now be described.

In the vibrato device 10 shown in FIG. 8. there is provided a lowfrequency oscillator 26 with the frequency of. for example. 30 Hz inaddition to the low frequency oscillator 16 of 7H2. The output signalsS.. from the os cillators l6 and 26 are applied through switches 21 and22 to a level control circuit 17 as its input signal.

The output signal from the audio amplifier 11 is further applied to adetector circuit 18 the output signal from which is applied to a timeconstant circuit 19 to be made as a DC signal which changes its level inresponse to the level of the audio signal (average level thereof). TheDC signal from the time constant circuit 19 is also fed to the levelcontrol circuit 17 as a control signal. Accordingly. the signal 5..passed through the level control circuit 17 from the oscillator 16 or 26is varied in level in response to the level of the audio signal.

For example. as the level of the audio signal increases. that of thesignal 5.. increases correspondingly. The signal 5.. which is controlledin level by the level control circuit 17 is applied to the pulseoscillator as a control signal for controlling the oscillationfrequencyfi, of the latter. Accordingly. the frequencyf of the pulses Paand Pb from the oscillator 15 is changed between. for example. 10 KHzand 30 KHz with the period the same as that of the signal S.. as shownin FIG. 4 by the solid line if the signal is high in level. whilechanged within a band narrower than the former as shown in FIG. 4 by thedotted line with the same period if the signal 5,. is low in level. As aresult. since the changing range of the delay time 1 of the BBD 12becomes wide if the audio signal is high in level. but becomes narrow ifthe audio signal is low in level. vibrato is applied to the singingvoice much as the singing voice is great in intensity. In this case. theperiod of vibrato can be varied by changing the switches 21 and 22.Accordingly. with the employment of the vibrato device 10 shown in FIG.8, a further specific effect can be applied to the microphone mixingcircuit.

As described above. with the present invention, a specific effect whichcan not be achieved by the prior art microphone mixing circuit can beapplied to the singing voice. and a user can enjoy the atmosphere that aprofessional singer is singing. Further. the present invention forachieving such effects is simple in construction and inexpensive.

The above description is given on the case that the BBD 12 is used asthe delay unit. but a CTD (charge transfer device) such as a CCD (chargecoupled device) can be used.

Further. it may be understood that such a system. as a flip-flop ormemory core may be used and that the delay time may be controlled by theclock pulse.

It may also be apparent that many modifications and variations could beeffected by those skilled in the art without departing from the spiritand scope of the novel concepts of the invention. and hence the scope ofthe invention should be determined by the appended claims only.

I claim as my invention:

1. An audio signal transmitting system comprising:

a. means for transferring audio signals;

b. means connected to an output stage of said transferring means forreproducing said audio signals:

and

c. means connected to said transferring means and supplied with clockpulses for delaying and frequency modulating said audio signals inresponse to the frequency of said clock pulses thereby to cause vibratoin the reproduced audio signals. a clock pulse oscillator for supplyingsaid clock pulses. a low frequency oscillator for applying a lowfrequency signal to said clock pulse oscillator. and a detector fordetecting an audio signal in said transferring means. the output signalfrom said detector being used to vary the level of said low frequencysignal and hence to control the oscillation of said clock pulses.

2. An audio signal transmitting system according to claim 1. whichfurther includes a time constant circuit which is connected to theoutput stage of said detector.

3. An audio transmitting system comprising, a first source of audiosignals. a vibrato device receiving the output of said source of audiosignals. said vibrato device comprising a variable time delay devicehaving an input terminal receiving said audio signals. an outputterminal. and at least one time delay control terminal. a pulseoscillator connected to said time delay control terminal to vary thetime delay of said variable time delay device; a low frequencyoscillator connected to said pulse oscillator to vary the pulsefrequency thereof. a second audio frequency source having left and rightstereo components. a first mixer receiving one of said left and rightstereo components of said second audio source and said first source ofaudio signals, a first audio producing means connected to said firstmixer. a second mixer receiving the other one of said left and rightstereo components of said second audio source and the output of saidvariable time delay device. and a second audio reproducing meansconnected to said second mixer.

4. An audio transmitting system according to claim 3 including a lowpass filter in said vibrato device connected between and said mixer andthe output terminal of said variable time delay device.

5. An audio transmitting system according to claim 3 including an matrixconnected between said first and second mixers and receiving said leftand right stereo components so as to vary their phases.

6. An audio transmitting system comprising. a first source of audiosignals. a vibrato device receiving the output of said source of audiosignals. said vibrato device comprising a variable time delay devicehaving an input terminal receiving said audio signals. an outputterminal. and at least one time delay control terminal.

a pulse oscillator connected to said time control terminal to vary thetime delay of said variable time delay device. a low frequencyoscillator connected to said pulse oscillator to vary the pulsefrequency thereof. a second audio frequency source having left and rightstereo components. a first mixer receiving one of said left and rightstereo components of said second audio source and the output of saidvariable time delay device. a first audio reproducing means connected tosaid first mixer. a second mixer receiving the other one of said leftand right stereo components of said second audio source and the outputof said variable time delay device. and a second audio reproducing meansconnected to said second mixer.

7. An audio transmitting system comprising. a source of left and rightstereocomponent signals. a matrix receiving said left and right stereocomponent signals and producing three output signals with one being asum of the left and right stereo component signals. another being aphase shifted left stereo component signal and the third being a phaseshifted right stereo component signal. a first mixer receiving said sumof the left and right stereo component signals and the phase shiftedleft stereo component signal from said matrix. a second mixer receivingsaid sum of the left and right stereo component signals and the phaseshifted right stereo component signal from said matrix. a vibrato devicereceiving said sum of the left and right stereo component signals fromsaid matrix. said vibrato device comprising a variable time delay devicehaving an input terminal receiving said sum of the left and right stereocomponent signals. an output terminal and at least one time delaycontrol terminal. a pulse oscillator connected to said time delaycontrol terminal to vary the time delay of said variable time delaydevice. a low frequency 05- cillator connected to said pulse oscillatorto vary the pulse frequency thereof. the output terminal of saidvariable time delay device supplying inputs to said first and secondmixers. a first audio reproducing means connected to said first mixer.and a second audio reproducing-means connected to said second mixer.

8. A vibrato device comprising a delay unit receiving an audio signal onits input terminal. said delay unit having an output terminal and atleast one time delay control terminal, a pulse oscillator connected tosaid time delay control terminal. a level control connected to the inputof said pulse oscillator to control its frequency. a detector receivingsaid audio signal, a time constant circuit receiving the output of saiddetector and supplying an input to said level control. and a first lowfrequency oscillator supplying an input to said level control.

9. A vibrato device according to claim 8 further including a second lowfrequency oscillator connected to said level control.

1. An audio signal transmitting system comprising: a. means fortransferring audio signals; b. means connected to an output stage ofsaid transferring means for reproducing said audio signals; and c. meansconnected to said transferring means and supplied with clock pulses fordelaying and frequency modulating said audio signals in response to thefrequency of said clock pulses thereby to cause vibrato in thereproduced audio signals, a clock pulse oscillator for supplying saidclock pulses, a low frequency oscillator for applying a low frequencysignal to said clock pulse oscillator, and a detector for detecting anaudio signal in said transferring means, the output signal from saiddetector being used to vary the level of said low frequency signal andhence to control the oscillation of said clock pulses.
 2. An audiosignal transmitting system according to claim 1, which further incluDesa time constant circuit which is connected to the output stage of saiddetector.
 3. An audio transmitting system comprising, a first source ofaudio signals, a vibrato device receiving the output of said source ofaudio signals, said vibrato device comprising a variable time delaydevice having an input terminal receiving said audio signals, an outputterminal, and at least one time delay control terminal, a pulseoscillator connected to said time delay control terminal to vary thetime delay of said variable time delay device, a low frequencyoscillator connected to said pulse oscillator to vary the pulsefrequency thereof, a second audio frequency source having left and rightstereo components, a first mixer receiving one of said left and rightstereo components of said second audio source and said first source ofaudio signals, a first audio producing means connected to said firstmixer, a second mixer receiving the other one of said left and rightstereo components of said second audio source and the output of saidvariable time delay device, and a second audio reproducing meansconnected to said second mixer.
 4. An audio transmitting systemaccording to claim 3 including a low pass filter in said vibrato deviceconnected between and said mixer and the output terminal of saidvariable time delay device.
 5. An audio transmitting system according toclaim 3 including an matrix connected between said first and secondmixers and receiving said left and right stereo components so as to varytheir phases.
 6. An audio transmitting system comprising, a first sourceof audio signals, a vibrato device receiving the output of said sourceof audio signals, said vibrato device comprising a variable time delaydevice having an input terminal receiving said audio signals, an outputterminal, and at least one time delay control terminal, a pulseoscillator connected to said time control terminal to vary the timedelay of said variable time delay device, a low frequency oscillatorconnected to said pulse oscillator to vary the pulse frequency thereof,a second audio frequency source having left and right stereo components,a first mixer receiving one of said left and right stereo components ofsaid second audio source and the output of said variable time delaydevice, a first audio reproducing means connected to said first mixer, asecond mixer receiving the other one of said left and right stereocomponents of said second audio source and the output of said variabletime delay device, and a second audio reproducing means connected tosaid second mixer.
 7. An audio transmitting system comprising, a sourceof left and right stereo component signals, a matrix receiving said leftand right stereo component signals and producing three output signalswith one being a sum of the left and right stereo component signals,another being a phase shifted left stereo component signal and the thirdbeing a phase shifted right stereo component signal, a first mixerreceiving said sum of the left and right stereo component signals andthe phase shifted left stereo component signal from said matrix, asecond mixer receiving said sum of the left and right stereo componentsignals and the phase shifted right stereo component signal from saidmatrix, a vibrato device receiving said sum of the left and right stereocomponent signals from said matrix, said vibrato device comprising avariable time delay device having an input terminal receiving said sumof the left and right stereo component signals, an output terminal andat least one time delay control terminal, a pulse oscillator connectedto said time delay control terminal to vary the time delay of saidvariable time delay device, a low frequency oscillator connected to saidpulse oscillator to vary the pulse frequency thereof, the outputterminal of said variable time delay device supplying inputs to saidfirst and second mixers, a first audio reproducing means connected tosaid first mixer, and a second audio reproducing means connected to Saidsecond mixer.
 8. A vibrato device comprising a delay unit receiving anaudio signal on its input terminal, said delay unit having an outputterminal and at least one time delay control terminal, a pulseoscillator connected to said time delay control terminal, a levelcontrol connected to the input of said pulse oscillator to control itsfrequency, a detector receiving said audio signal, a time constantcircuit receiving the output of said detector and supplying an input tosaid level control, and a first low frequency oscillator supplying aninput to said level control.
 9. A vibrato device according to claim 8further including a second low frequency oscillator connected to saidlevel control.